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This! Or reserve just one spot for semi-randomly selected post from promoted and the more was spent on promotion the higher the chance that this post will be selected. Obviously every trending website load/view would mean new roll.

With that solution you only get a few promoted posts that people's eyes will be on. If the posts are inside content creators posts. The way Google Ads work. Then the model scales. Because there are thousands of eyes looking at specific posts than the trending page. YouTube has a an ad post below a YouTube content creators video. It scales and works. Because people visit content creators more than they visit a trending page

Sure, something like that could be done as well.